1. Field of the Invention
This invention relates to applications pertaining to the analysis of noninvasive dynamic near-infrared optical tomography measures of a target system. More particularly, the invention includes the assessment of the target system response and modulation by simultaneously measuring the coordinated interaction between multiple sites of the target system.
2. Description of the Related Art
Many techniques and systems have been developed to image the interior structure of a turbid medium through the measurement of energy that becomes scattered upon being introduced into a medium. Typically, a system for imaging based on scattered energy detection includes a source for directing energy into the target medium and a plurality of detectors for measuring the intensity of the scattered energy exiting the target medium at various locations with respect to the source. Based on the measured intensity of the energy exiting the target medium, it is possible to reconstruct an image representing the cross-sectional scattering and/or absorption properties of the target. Exemplary methods and systems are disclosed in Barbour et al., U.S. Pat. No. 5,137,355, entitled “Method of Imaging a Random Medium,” (hereinafter the “Barbour 355 patent”), Barbour, U.S. Pat. No. 6,081,322, entitled “NIR Clinical Opti-Scan System,” (hereinafter the “Barbour 322 patent”), and Barbour PCT applications PCT/US00/25156; PCT/US00/25151; PCT/US00/25155 and PCT/US00/25136, all of which are incorporated herein by reference.
Imaging techniques based on the detection of scattered energy are capable of measuring the internal absorption, scattering and other properties of a medium using sources whose penetrating energy is highly scattered by the medium. Accordingly, these techniques permit the use of wavelengths and types of energy not suitable for familiar transmission imaging techniques. Thus they have great potential for detecting properties of media that are not accessible to traditional energy sources used for transmission imaging techniques. For example, one flourishing application of imaging in scattering media is in the field of optical tomography. Optical tomography permits the use of near infrared energy as an imaging source. Near infrared energy is highly scattered by human tissue and is therefore an unsuitable source for straight-line transmission imaging in human tissue (e.g., x-ray imaging). However, these properties make it a superior imaging source for scattering imaging techniques. The ability to use near infrared energy as an imaging source is of particular interest in clinical medicine because it is exceptionally responsive to blood volume and blood oxygenation levels, thus having great potential for detecting cardiovascular disease, tumors and other disease states.
A continuing goal of medical procedures is to obtain objective measures of the state of health and disease. Broadly speaking these measures can be grouped into two classes; those that are performed at a discrete point in time and those that involve essentially continuous measures for a period of time. Examples of the former include many types of blood and urine analyses, tissue biopsy studies, and most forms of medical imaging studies. Prominent examples of the latter include electroencephalographic (EEG) and electrocardiographic (ECG) measures as well as some forms of medical imaging. Common to these is the notion that the information sought after is some assessment of tissue function. When performing such measures it is often desirable, if not essential, to employ noninvasive methods, else the procedure itself can severely bias the measurement. Another feature of these studies is that the measurement employed typically is restricted to providing information about a specific end-organ, usually the heart or brain. More broadly speaking it would be highly desirable, within the capabilities of a single noninvasive measuring technology, to obtain functional information regarding the state of health or disease of specific sites in the body as well as information regarding the coordinated interaction between a target tissue and other body sites. The latter holds relevance, because in many disease states (diabetes, other endocrine and hemotologic disorders, autoinimune, some forms of cancer), the main affliction is considered to originate from a dysregulation in coordinated activities (e.g., autonomic disorders).
Practical realization of these aims poses a number of technical and conceptual challenges. In particular, various known imaging techniques, such as x-ray, magnetic resonance, ultrasound, and positron emission technology (PET) do not lend themselves to assessing the coordinated interaction between a target tissue and other body sites.